Controlling the compositional matrix of pyrogenic products using carbon dioxide in the pyrolysis of agricultural plastic waste

Abstract

Plastics are extensively employed in agriculture, generating an enormous volume of plastic waste. This study investigated the pyrolysis of silage film waste (SFW) to enable its conversion into energy/value-added chemicals. CO2 was chosen as the reactive medium to provide green pyrolysis. Nevertheless, the results showed that most of the carbon in the SFW was assigned to wax-like oil formed by thermal cracking. It was presumed that the reactivity of CO2 was effective only under certain optimal temperature conditions. To this end, the test setup was modified to increase the residence time of the reactants (CO2 and volatiles from SFW). With respect to inert gas conditions, syngas formation was observed under CO2 conditions. The enhanced formation of syngas was realised by the simultaneous reduction of CO2 into CO and the oxidation of volatiles into CO. CO2 also enhances the thermal cracking of volatiles, leading to enhanced formation of C2-hydrocarbons. These features provide an effective means of decreasing the aromaticity of oil from SFW pyrolysis. The simultaneous reduction of CO2 into CO and oxidation of volatiles into CO block the mechanistic pathway to form polycyclic aromatic hydrocarbons. CO enhancement by CO2 offers an effective means for abating the fate of toxic chemicals.